Ehh! I wonder, when somebody remember, ms-dos was NOT first to use such tricks. - All these stuff was REimplemented on PC IBM's technology of overlays, created

Ehh! I wonder, when somebody remember, ms-dos was NOT first to use such tricks. - All these stuff was REimplemented on PC IBM's technology of overlays, created as marketing technology, to widen line of IBM mainframes, as top models have enough RAM to work with programs directly, but cheapest models have to use something like virtual memory and swap on magnetic drum, to use same software. And sure, when IBM PC achieved wide adoption, people also sought, some things could be done on PC, what before done on mainframes or mini-computers, but much cheaper. I exactly seen revolution in approx 1993-1994, when prices on RAM dropped and become possible to equip PC with 1M or even more. Unfortunately I myself believed, to talks of older colleagues, that all these PC tricks are not serious, and IBM is strong and will return with something much more powerful :) I even not imagined, about current 64-bit PCs and what opportunities they opened.